As I understand it, Cooper pairs form between two fermions and are the cause of superconductivity. I was told by a teacher that the formation of Cooper pairs and BCS theory requires both fermions to be charged. But I also understand that Cooper pairs can form between two neutrons in neutron stars and neutrons are neutral particles. I asked the teacher the same question and they told me that it was because of pairing between the quark constituents of the neutron.
However, I have not been able to find any article or text that refers to this. In reading about BCS theory I have also not found any discussion on the fermions needing to be charged. Could someone refer me to any such text? Or help me understand what I am missing. I am new to the subject and asking questions as a novice.
The context of the discussion was that the teacher was saying that neutron star superconductivity and superfluidity required QED to be described. And I could not understand how QED could be applied to neutrons.